Electrospray printing of graphene layers for chemiresistive gas sensors

In this work we investigate the electrospray technique for the preparation of graphene layers for use in chemiresistive gas sensors. A dispersion of reduced graphene oxide (rGO) in isopropanol (0,1 mg/ml) is electrosprayed and the rGO sheets are deposited onto a polymeric substrate with printed interdigitated electrodes. The size of the rGO spot is determined to a large extent by the distance between the needle tip and the substrate, whereas the deposition pattern strongly depends upon the applied voltage and the flow rate, which determine the electrospray operation regime. The optimal process parameters for obtaining uniform rGO layers over the entire surface of the interdigitated electrodes (active area of the sensor) have been determined. The performance of the sensors based on electroprayed rGO for the detection at room temperature of sub-ppm levels of nitrogen oxide (NO₂), ozone (O₃) and carbon monoxide (CO) in air has been assessed, including the effects of air humidity and UV light irradiation.